1. Field of the Invention
The present invention relates to a winged angled needle assembly for constituting a port access infusion set, called PAIS) to be used for blood dialysis, fluid infusion, blood infusion, etc., and it relates particularly to a winged angled needle assembly improved in the form of a protective portion.
For effecting blood dialysis, blood filtering, blood infusion, fluid infusion or the delivery of a therapeutic fluid such as an anticancer medication, insulin, or the like into a vascular system for a long period of time, there has been developed an advanced method in which an implanted port (subcutaneous implanted part) is provided under the surface of the skin of a patient and an angled needle is caused to subcutaneously pierce the implanted port, in place of a conventional direct subcutaneous delivery of the blood system of a patient. PAIS is a device for use in a method using the above implanted port. The winged angled needle assembly is the needle suitably used in the PAIS and has a configuration in which the portion of the needle including a forward end portion to pierce the implanted port, is angularly disposed at approximately 90 degrees relative to a proximal end portion which is formed to join the support in the needle assembly.
In recent years, with the prevalence of infectious diseases that are taken on through such medical needles tainted with carriers' blood or body fluid, such as viral hepatitis, AIDS, etc., it is a very important task in medical facilities to prevent such infections caused by accidental needle-sticks to medical practitioners working on blood infusion, blood dialysis, etc., and environmental pollutions caused by disposal of infected needles.
With blood-stained needles, etc., to which blood is adhering, have very fine sizes, it is not always possible to prevent entirely accidental needle-sticks, wherein, a needle pierces the finger or hand of a medical practitioner whose finger(s) may come close to a needle end due to a subtle mistake in visual observation, even if he or she is considerably careful. From this point of view, it is strongly demanded that the winged angled needle assembly should be so structured to have mechanism or means for preventing accidental needle-sticks or protecting practitioners from accidental needle-sticks.
2. Description of the Related Art
U.S. Pat. No. 5,951,522 to Rosato et al discloses a hypodermic needle having mounted thereon a wing assembly which can take the form of a single integral member having a plurality of spaced apart fold lines which permits the integral member to be folded between a mounting position and a protective position or a pair of wing members which are mounted in a scissors arrangement which is movable between a mounting position and a protective position.
In the invention of Rosato et al, when the hypodermic needle is in an installed position (in a state where the angled needle is caused to pierce the port and a therapeutic fluid such as an anticancer medication or the like is infused), the wing assembly is folded perpendicular to the angled needle that is angled at 90 degrees relative to the hub. Further, when it is in a protective position (in a state where the angled needle is caused to pierce the port or it is pulled out of the port and discarded after infusion of the therapeutic fluid), the wing assembly extends in parallel with the angled needle and the angled needle is in a state where it is encased in the wing assembly.
However, the winged angled needle assembly (hypodermic needle) of Rosato et al still has some problems to solve. That is, (1) the size of the above wing assembly limits the usable length of the angled needle in the invention of Rosato et al. When the length of the angled needle is so limited, the application of the winged angled needle assembly to various patients is no longer possible since the depth of the subcutaneously implanted port differs among patients, so that its therapeutic application is limited. (2) When the angled needle of Rosato et al is pulled out of the implanted port after its use, a practitioner grabs (closes) the wing assembly with his or her index or middle finger and thumb, thereby to pull the angled needle out of the port and prevent accidental needle-sticks at the same time. However, when the above angled needle is inserted very tightly into the implanted port with no space between the needle and the port (for example, when the angled needle is inserted with pressure so tightly as the circumferential surface of the angled needle presses and outwardly open the cross-sectional portions of the wall of the port laterally), considerable power is required to pull the angled needle out of the port. However, it is difficult to grab and properly operate the above wing assembly with the index or middle finger and thumb of only one hand. This situation involves a problem that when a medical practitioner takes more time, handling the winged angled needle assembly, the more pain a patient is inflicted.
U.S. Pat. No. 6,500,155 to Sasso discloses a winged angled needle assembly comprising an angled needle and a pair of wing members mounted to side portions of the angled needle, in which channels for confining the distal end portion of the angled needle are formed in the wing members and the wing members are folded together towards the distal end portion of the angled needle to confine the distal end portion of the needle.
However, the winged angled needle assembly of Sasso has a problem that the accidental needle-sticks cannot be prevented simultaneously with pulling the angled needle out of the implanted port. In the state of the art with respect to recent winged angled needle assemblies, it is required to provide means capable of preventing accidental needle-sticks simultaneously in the process of pulling out the angled needle out of the implanted port. In U.S. Pat. No. 6,500,155 to Sasso, however, nothing is disclosed with regard to any effective means that can satisfy the above requirement for preventing accidental needle-sticks.
U.S. Pat. No. 5,584,813 to Livingston et al discloses a subcutaneous injection set (winged angled needle assembly) for subcutaneous placement of a distal end of a soft flexible cannula formed of a polytetrafluoroethylene tube, or the like, said injection set comprising a longitudinally collapsible injector and an insertion needle formed of a metal and having an eye formed therein for threaded reception of said distal end of said cannula.
In the winged angled needle assembly of Livingston et al, however, it is the soft flexible cannula that is inserted into the implanted port, and this cannula is inserted into the port, together with the insertion needle formed of a metal. That is, the cannula is inserted into, and implanted in, the port in a manner in which a thread (cannula) is passed through the eye of a needle (needle formed of a metal), and then, the needle formed of a metal is withdrawn and discarded in a state wherein the needle is encased in the collapsible injector.
(1) In the winged angled needle assembly of Livingston et al, however, the use of the insertion needle formed of a metal is essential, so that there is a risk of the cannula being damaged to form a pinhole when the cannula is inserted into the implanted port together with the needle formed of a metal. Further, it is difficult to insert the cannula smoothly into the implanted port by sliding the cannula through the hollow portion of the needle formed of a metal.
(2) When the cannula is formed of a PTFE tube, the cannula is easily kinked when made extremely curved, and the kinking may impair the infusion of therapeutic fluid. Further, there is another problem that the cannula formed of a flexible PTFE tube may be decreased in internal diameter due to a repulsive pressure exerted by the insertion portion (septum, or the like) of the implanted port formed from an elastomeric material such as a silicone rubber, or the like, which may impair or block the smooth infusion of therapeutic fluid.
(3) Further, when the collapsible injector unintentionally collapses while a practitioner is at work, the tip of the needle formed of a metal placed in the collapsible injector may become exposed accidentally and dangerously since the injector has no stopper to prevent it.